Array of geiger-mode avalanche photodiodes for detecting infrared radiation

Abstract

An array of Geiger-mode avalanche photodiodes is formed in a die and includes: an internal dielectric structure, arranged on the die; and an external dielectric region arranged on the internal dielectric structure. The external dielectric region is formed by an external material that absorbs radiation having a wavelength that falls in a stop-band with low wavelength and transmits radiation having a wavelength that falls in a pass-band with high wavelength, at least part of the pass-band including wavelengths in the infrared. The internal dielectric structure is formed by one or more internal materials that substantially transmit radiation having a wavelength that falls in the stop-band and in the pass-band and have refractive indices that fall in an interval having an amplitude of 0.4. In the stop-band and in the pass-band the external dielectric region has a refractive index with the real part that falls in the above interval.

The invention claimed is: 
     
       1. An optoelectronic device, comprising:
 a first array of Geiger-mode avalanche photodiodes, said first array being formed in a die; and 
 a packaging structure, which includes: 
 an internal dielectric structure arranged on the die, in direct contact therewith, and overlying said photodiodes; and 
 a first external dielectric region arranged on the internal dielectric structure, in direct contact therewith; wherein:
 said first external dielectric region is formed by a first material that absorbs radiation having a wavelength that falls in a stop-band with a first wavelength range and transmits radiation having a wavelength that falls in a pass-band with a second wavelength range that is higher than the first wavelength range, at least part of said pass-band including infrared wavelengths; 
 said internal dielectric structure is formed by one or more second materials that substantially transmit radiation having a wavelength that falls in said stop-band and in said pass-band and have refractive indices that fall in an interval having a width of 0.4; and 
 in said stop-band and in said pass-band, said first external dielectric region has a refractive index with a real part that falls within said interval. 
 
 
     
     
       2. The optoelectronic device according to  claim 1 , wherein said internal dielectric region comprises a first layer made of an epoxy resin and arranged on the die. 
     
     
       3. The optoelectronic device according to  claim 2 , wherein the first layer surrounds the die laterally. 
     
     
       4. The optoelectronic device according to  claim 2 , wherein said internal dielectric region comprises a second layer that bonds the first layer and the first external dielectric region together. 
     
     
       5. The optoelectronic device according to  claim 1 , wherein said first external dielectric region is made of a polymeric plastic material. 
     
     
       6. The optoelectronic device according to  claim 5 , wherein said first external dielectric region is made of allyl diglycol carbonate or polyallyl diglycol carbonate. 
     
     
       7. The optoelectronic device according to  claim 1 , wherein said die comprises a semiconductor body having a front surface and forming a cathode region of a first type of conductivity; and wherein each photodiode comprises:
 a respective anode region of a second type of conductivity, which extends within the cathode region; and 
 a lateral insulation region extending through the body starting from the front surface and surrounding the respective anode region and a corresponding part of the cathode region, said lateral insulation region including a barrier region and an insulating region, which surrounds the barrier region, said barrier region being configured to absorb or reflect radiation. 
 
     
     
       8. The optoelectronic device according to  claim 7 , wherein said anode region extends into the semiconductor body from the front surface. 
     
     
       9. The optoelectronic device according to  claim 7 , wherein said die comprises a passivation region, which extends over the front surface, in contact with the semiconductor body; and wherein said internal dielectric structure extends in contact with said passivation region. 
     
     
       10. The optoelectronic device according to  claim 9 , wherein said passivation region has a refractive index, which, in said stop-band and in said pass-band, falls in said interval. 
     
     
       11. The optoelectronic device according to  claim 1 , further comprising:
 a second array of Geiger-mode avalanche photodiodes; and 
 a second external dielectric region overlying said second array and made of a third material having a different pass-band than the first material. 
 
     
     
       12. The optoelectronic device according to  claim 1 , wherein said packaging structure forms a surface-mount packaging. 
     
     
       13. A photon-detection system comprising:
 an optoelectronic device that includes:
 a first array of Geiger-mode avalanche photodiodes, said first array being formed in a die and 
 a packaging structure that includes an internal dielectric structure arranged on the die, in direct contact therewith, and overlying said photodiodes; and a first external dielectric region arranged on the internal dielectric structure, in direct contact therewith; 
 
 a light source optically coupled to the first array; and 
 a processing unit electrically coupled to the first array, wherein:
 said first external dielectric region is formed by a first material that absorbs radiation having a wavelength that falls in a stop-band with a first wavelength range and transmits radiation having a wavelength that falls in a pass-band with a second wavelength range that is higher than the first wavelength range, at least part of said pass-band including infrared wavelengths; 
 said internal dielectric structure is formed by one or more second materials that substantially transmit radiation having a wavelength that falls in said stop-band and in said pass-band and have refractive indices that fall in an interval having a width of 0.4; and 
 in said stop-band and in said pass-band, said first external dielectric region has a refractive index with a real part that falls within said interval. 
 
 
     
     
       14. The photon-detection system according to  claim 13 , wherein said processing unit comprises a microcontroller unit, or else a discriminator and a counter electrically coupled together. 
     
     
       15. The photon-detection system according to  claim 13 , wherein said die comprises a semiconductor body having a front surface and forming a cathode region of a first type of conductivity; and wherein each photodiode comprises:
 a respective anode region of a second type of conductivity, which extends within the cathode region; and 
 a lateral insulation region extending through the body starting from the front surface and surrounding the respective anode region and a corresponding part of the cathode region, said lateral insulation region including a barrier region and an insulating region, which surrounds the barrier region, said barrier region being configured to absorb or reflect radiation. 
 
     
     
       16. The photon-detection system according to  claim 13 , wherein the optoelectronic device includes:
 a second array of Geiger-mode avalanche photodiodes; and 
 a second external dielectric region overlying said second array and made of a third material having a different pass-band than the first material. 
 
     
     
       17. An optoelectronic device, comprising:
 a first array of Geiger-mode avalanche photodiodes configured to detect incoming photons and emit secondary photons that have a wavelength in a first wavelength range between 400 nm and 600 nm; 
 a packaging structure, which includes: 
 an internal dielectric structure arranged on the first array and overlying said photodiodes; and 
 a first external dielectric region arranged on the internal dielectric structure, in direct contact therewith; wherein:
 said first external dielectric region is formed by a first material that absorbs the secondary photons in the first wavelength range and transmits radiation having a wavelength that falls in a pass-band with a second wavelength range that is higher than the first wavelength range, at least part of said pass-band including infrared wavelengths; and 
 said internal dielectric structure is formed by one or more second materials that substantially transmit radiation having a wavelength that falls in either of said first and second wavelength ranges. 
 
 
     
     
       18. The optoelectronic device according to  claim 17 , comprising a semiconductor body having a front surface and forming a cathode region of a first type of conductivity; and wherein each photodiode comprises:
 a respective anode region of a second type of conductivity, which extends within the cathode region; 
 a lateral insulation region extending through the body starting from the front surface and surrounding the respective anode region and a corresponding part of the cathode region, said lateral insulation region including a barrier region and an insulating region, which surrounds the barrier region, said barrier region being configured to absorb or reflect radiation. 
 
     
     
       19. The optoelectronic device according to  claim 18 , comprising a passivation region, which extends over the front surface, in contact with the semiconductor body; and wherein said internal dielectric structure extends in contact with said passivation region and said passivation region, first external dielectric region, and internal dielectric structure each have a refractive index that falls in an interval having a width of 0.4. 
     
     
       20. The optoelectronic device according to  claim 17 , further comprising:
 a second array of Geiger-mode avalanche photodiodes; and 
 a second external dielectric region overlying said second array and made of a third material having a different pass-band than the first material.